The present invention relates generally to an imaging apparatus and compositions useful as layers for film components thereof, for use in electrostatographic, including digital, apparatuses. The compositions herein are useful for many purposes including layers for fixing films, bias transfer films, intermediate transfer films, transfix films, and the like. More specifically, the present invention relates to compositions comprising a haloelastomer and a doped metal oxide conductive filler in order to impart a desired resistivity wherein, in embodiments, the resistivity is stable to changes in the environment, such as changes in relative humidity and temperature. In specific embodiments, the doped metal oxide conductive filler is an antimony doped tin oxide filler. The compositions of the present invention may be useful in films used in xerographic machines, especially color machines.
In a typical electrostatographic reproducing apparatus, a light image of an original to be copied is recorded in the form of an electrostatic latent image upon a photosensitive member and the latent image is subsequently rendered visible by the application of electroscopic thermoplastic resin particles which are commonly referred to as toner. The visible toner image is then in a loose powdered form and can be easily disturbed or destroyed. The toner image is usually fixed or fused upon a support which may be the photosensitive member itself or other support sheet such as plain paper.
In many of the components useful in the xerographic process, it is desirable to be able to tailor the resistivity of layers of components for proper and efficient workability. In addition, it is desirable that the resistivity of the components remain relatively constant and that the resistivity not be sensitive to changes in the environment, such as changes in temperature and/or relative humidity. Therefore, it is desirable that the resistivity of layers useful in xerographic components be controlled.
Attempts at controlling the conductivity of layers, especially outer layers, of components, have been accomplished by, for example, adding conductive fillers such as ionic additives to the surface layer of the components. However, to some extent, there are problems associated with the use of these additives. In particular, undissolved particles frequently bloom or migrate to the surface of a polymer and cause an imperfection in the polymer. This leads to a nonuniform resistivity, which in turn, leads to poor antistatic properties and poor mechanical strength for layers using the filled polymers. The ionic additives on surface layers may interfere with toner release and affect toner offset when the filled polymers are used as layers for intermediate transfer members, fuser members, bias transfer members, transfix members, and the like. The higher temperatures of the fusing process also increase the mobility of the ionic components and increase depletion rates. Furthermore, bubbles appear in the conductive polymer, some of which can only be seen with the aid of a microscope, others of which are large enough to be observed with the naked eye. These bubbles provide the same kind of difficulty as the undissolved particles in the polymer namely, poor or nonuniform electrical properties and poor mechanical properties.
In addition, the ionic additives themselves are sensitive to changes in temperature, humidity, operating time and applied field. These sensitivities often limit the resistivity range. For example, the resistivity usually decreases by up to two orders of magnitude or more as the humidity increases from 20% to 80% relative humidity. This effect limits the operational or process latitude.
Moreover, ion transfer can also occur in these systems. The transfer of ions will lead to contamination problems, which in turn, can reduce the life of the machine. Ion transfer also increases the resistivity of the polymer member after repetitive use. This can limit the process and operational latitude and eventually the ion-filled polymer component will be unusable.
Use of carbon black as a conductive filler has also been disclosed. Carbon black has been the chosen additive for imparting conductive properties in electrostatographic films. Carbon black is relatively inexpensive and very efficient in that a relatively small percentage can impart a high degree of conductivity. However, in practice with this material, it difficult and sometimes impossible to fabricate products with the desired level of conductivity. Further, films filled with carbon black have a tendency to contaminate their surroundings with black, conductive debris. In particular, the carbon black can cause undesirable black marks on the copied or printed substrates. Carbon black particles can also impart other specific adverse effects. Such carbon dispersions are difficult to prepare due to carbon agglomeration, and the resulting layers may deform due to random hard carbon agglomerate formation sites as well as non-uniform electrical properties. This can lead to an adverse change in the conformability of the layer.
Many doped metal oxides offer significant advantages in both color and transparency when compared to carbon black. They are, however, relatively expensive and usually require higher dosages to achieve comparable levels of conductivity. In addition, dispersion of metal oxides can lead to short comings in surface roughness and particle size.
U.S. Pat. No. 5,147,751 discloses that a polyurethane with antimony doped tin oxide filler may be used as the outer protective layer of a photoreceptor. The patent also discloses that the outer layer may be comprised of a fluoroplastic binder resin.
U.S. Pat. No. 4,426,435 discloses an electrophotographic light-sensitive member comprising a conductive support, a photoconductive layer and a protective outer layer, wherein the protective outer layer may be comprised of a binder of, for example, fluorocarbon or polyurethane, and a filler, such as, for example, antimony doped tin oxide.
U.S. Pat. No. 5,503,955 discloses the use of antimony doped tin oxide in polyurethane or polyimide as an adhesive in a photoreceptor.
U.S. Pat. No. 5,635,327 discloses a photoreceptor having a surface layer comprised of a dried and/or cured product under a reduced pressure of an inorganic or organic high molecular weight material and a conductive metal oxide dispersed therein. The high molecular weight resin is disclosed as, for example, fluororesin, polyurethane or polyimide, and the conductive filler is disclosed as, for example, antimony doped tin oxide.
U.S. Pat. No. 5,585,905 discloses an intermediate toner transfer member comprising a substrate and an outer layer comprised of a fluoropolymer polymerized from a plurality of monomers, at least one monomer being an olefin having only carbon atoms and hydrogen atoms, and at least one monomer being fluorinated. The outer layer may include conductive particles such as antimony doped tin oxide.
Therefore, a need remains for compositions useful as layers for xerographic members for use in electrostatographic machines, wherein the layer possesses the desired resistivity without the drawbacks of lack of transparency of the layer which may adversely affect its use in color products, especially color imaging systems. Further, a need remains for a compositions useful in conductive films having conductive fillers which impart the desired resistivity without compromising surface roughness. Moreover, a need exists for compositions useful as layers in which the resistivity thereof is uniform and is relatively unaffected by changes in environmental conditions such as changes in humidity, temperature, and the like.